1. Field of the Invention
The present invention relates to a method for changing the level of oxygen or other gases dissolved in water and oxidation-reduction potential of water, and removing organic and inorganic substances contained in water and/or sterilizing bacteria contained in water in order to obtain water having a property suitable for usage in various kinds of industry.
2. Description of the Related Art
It is known that the potential of water is allowed to change through oxidation-reduction of the water, and the water is used for various kinds of industry or the like. An apparatus for the purpose is put into actual usage.
Then, the water obtained by such methods and/or apparatus is useful for the maintenance of the freshness of vegetables, and culture of agricultural products without using chemicals, and improvement in the cultural efficiency in the field of agriculture. In the field of marine products industry, the water can be efficiently used to maintain the freshness of fishery products, and to culture marine products without using chemicals.
Besides, in the field of stock raising, the water obtained with such methods and/or apparatus is effective for raising livestock without using chemicals, improving environment for the prevention of stock raising hazard, and maintaining the freshness of stock raising products. In the field of food industry, the water is useful for maintaining the freshness of food by allowing the use of oxygen-free water.
Furthermore, in the field of water purification industry, the treatment performance of drinking water and impure water is improved. Furthermore, in the field of brewing industry of alcoholic beverages, such water contributes to the improvement in the quality and productivity thereof. Still, in the field of medicine and pharmacy, the water contributes to the improvement in the efficacy of chemicals and improvement in the preventive medicine. In the manufacturing industry, the water is effective for prevention of oxidation by allowing the use of oxygen-free water as industrial water. In other fields, the water can be used in a wide range of usage for environmental improvement.
Besides, if treated water with the level of oxidation-reduction potential changes as mentioned above are free of organic and inorganic substances and bacteria, the usage thereof will be widened.
It is also known that feeding air into water and/or applying a sound wave to the water changes the level of oxidation-reduction potential of the water.
Furthermore, it is also known that injection of N2 gas in the water using the aeration method changes the level of oxidation-reduction potential of the water. FIG. 6 shows a change in the level of oxygen dissolved in the water thus obtained. In this figure, the vertical axis shows time (in hours), and the lateral axis shows the level of dissolved oxygen (DO) in the water (in PPM). Furthermore, FIG. 7 shows a change in the level of oxidation-reduction potential of the same water. The vertical axis shows time (in hours), and the lateral axis shows the level of oxidation-reduction potential (in 100 mV). Both in FIGS. 6 and 7, the injection of N2 gas starts at point A and ends at point B. Thereafter, the vessel containing the water is left as it stands in an open state. These figures indicate that the levels of dissolved oxygen and of the oxidation-reduction potential changes only marginally.
Then, in addition to injecting N2 gas into water contained in a tank using the aeration method as mentioned above, an oxidation-reduction potential controller is provided to change the level of oxidation-reduction potential of water. The oxidation-reduction potential controller includes a controller for controlling the amount of air or oxygen to be injected into the water and yet another controller for controlling the level of sound wave to be applied to the water. With these controllers included, the oxidation-reduction potential controller is designed to control and adjust the said amount of the air or oxygen and the said level of sound wave simultaneously. FIGS. 8 and 9 show the changes therein thus obtained.
In FIGS. 8 and 9, the injection of N2 gas starts at point A and halts at point B. Thereafter, a vessel containing the water is left as it stands in an open state. In FIG. 8, the vertical axis shows time (in hours), and the lateral axis shows the level of dissolved oxygen (DO) in the water (in PPM). As shown in FIG. 8, the level of dissolved oxygen decreased to near zero. FIG. 9 shows the level of oxidation-reduction potential of the same water. The vertical axis shows time (in hours), and the lateral axis shows the level of oxidation-reduction potential (in 100 mV). FIG. 9 indicates that the level of oxidation-reduction potential decreases immediately after the water is treated. With the vessel left as it stands, however, it comes back to the original level and even rises to a higher level, instead of getting stabilized.
Water has the property of taking in gases, which is referred to as gas dissolution. Natural water has every gaseous constituent of air such as nitrogen, oxygen, carbon dioxide, and the like dissolved therein. Among others, it is an important property of water to take in oxygen, namely to have oxygen dissolved therein because of its biogenic implications. Existence of bacteria as well as fish, plants and animals, and human beings entirely depends on dissolved oxygen. Dissolved oxygen has also much significance for the aquatic environments including rivers, ponds, lakes, seas, and the like. If there is a decrease in the level of dissolved oxygen in these waters, red tide can break out, causing mass grave of fish and shellfish. In rivers, if the level of dissolved oxygen lowers to 2 PPM or less, fish cannot make its habitat any more.
It is true that water temperature has a large effect on the level of oxygen dissolved in water At low water temperatures, the level of oxygen dissolved in water is larger, while at high water temperatures, it is lower, as shown in FIG. 10. In this figure, the lateral axis shows water temperature (in xc2x0 C.), and the vertical axis shows the level of dissolved oxygen (in PPM). Changing a partial pressure of oxygen in gas that comes in contact with water also causes a change in the level of dissolved oxygen. Changing an oxygen ratio in the gas can also change such level. Furthermore, it is known that some other changes in conditions have the same effect. For example, if water temperature is constant, the level of dissolved oxygen should remain constant. In natural water, however, there are observed changes in the level of dissolved oxygen for some unknown reason. A presumable explanation of this might be the effects of its crystal structure, i.e., clusters. Some component parts of the structure are more likely to take in oxygen, and others are not. It follows that it requires to control water temperature, oxygen pressure, oxygen ratio, and clusters (i.e., the crystal structure of water) in order to control the level of oxygen dissolved in natural water.
As stated above, the prior art provides an apparatus for obtaining water having a desired level with respect to either dissolved oxygen (DO) or the oxidation-reduction potential. However, the prior art provides no apparatus to meet the need to obtain water having a desired level for both of them. It may be safely said that there have yet been no methods for controlling the level of dissolved oxygen with accuracy and at a moderate cost in spite of its importance.
The applicant of this invention came up with a combination of an existing apparatus according to the prior art with a device for removing organic and inorganic substances and sterilizing bacteria contained in water. This is shown by the patent journal disclosing the Japanese patent number 2990574 issued to the same applicant. By further improving the prior art, the present invention provides a method for obtaining treated water having a desired level both for dissolved oxygen and oxidation-reduction potential. The method of the present invention is also capable of removing organic and inorganic substances contained in water and sterilizing bacterial contained therein, thereby facilitating treatment processes efficiently.
According to the present invention, the above problem can be solved by providing a method comprising the steps of:
supplying crude water to a water retention chamber of a closed type tank with an automatic water supply device to obtain a predetermined amount of retained water;
mixing air or oxygen and nitrogen gas with the retained water in the closed type tank at a predetermined mixing ratio, and simultaneously feeding the gas mixed water into a circulation channel for circulating the retained water in the closed type tank through a pressure tank by means of a pressure pump;
circulating the retained water in the closed type tank in a circulation channel by means of a circulating pump, and activating the water by means of a ceramic pipe and an infrared ray irradiation device both of which are arranged in the circulation channel, thereby injecting the resulting activated water in the retained water in the closed type tank by means of a gas injection nozzle;
adjusting the mixing ratio at which air or oxygen and nitrogen gas is mixed with the retained water in the closed type tank by means of a device for adjusting the levels of oxidation-reduction potential and dissolved oxygen according to the level detected by a sensor for detecting the levels of oxidation-reduction potential and dissolved oxygen, and changing the revolution number of the said pressure pump by means of a pump motor controller to change the pressure in the said pressure tank, and changing the revolution number of the said circulating pump to change the injection pressure of the said gas injection nozzle;
filtering sludge or the like by allowing the retained water in the closed tank to pass through a filtering device by means of filtering pump and further allowing the water to pass through a ceramic-filled device thereby adjusting oxidation-reduction potential of the water to a desired level and still further allowing the water to pass through an ultraviolet ray irradiation device for sterilization followed by bringing back the water to the closed type tank; and,
taking out the treated water in the closed type tank.
Besides, according to the present invention, the above problem can also be solved by providing the above mentioned method further comprising the steps of:
taking out the treated water in the closed type tank from the outlet port of treated water in the closed type tank and leading the treated water to a storage tank, the storage tank being equipped with a liquid-level adjusting means and a water supply pump controlled by the liquid-level adjusting means to maintain the amount of to be placed in storage to a predetermined value; and,
taking out the treated water from the storage tank.
Besides, according to the present invention, the above problem can also be solved by configuring the above steps so that the gas mixed water having air or oxygen and nitrogen gas mixed at a predetermined mixing ratio is sucked in the circulation channel through the use of a negative pressure in the pressure tank.
Furthermore, according to the present invention, the above problem can also be solved by configuring the above steps so that the variable nitrogen/oxygen mixing ratio method is used to control the level of dissolved oxygen.